The most reasonable is that both torrents have the same hash.
Like you download a torrent from a Nexusphp-based tracker A or a Gazelle-based tracker B and upload it to another Gazelle-based tracker C. Because tracker C does not change the torrent's hash, so when you re-download that uploaded torrent from tracker C, its hash is still the same as the downloaded from tracker A or tracker B.
If you force seeding that torrent on both tracker A and tracker C, your client will send statistic to both trackers, especially when there is someone downloading that torrent, your upload will be wrongly recorded. Both trackers will find out that you are cheating.
- Don't ever seed torrents which have the same hash on the same client.
- Don't upload torrents the hash of which have not been modified or will surely not be modified.

P/S: if you find the same problem on any trackers, please report it to their staff to solve the problem. In some cases, the uploader may be warned or banned, but your action will save all the rest of us. Sure that you will not tolerate cheating or cheating-related, right?